Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$107.88	9.698%	$118.3422	$118.34	$118.35	$118.30
Purchase #2	$160.75	6.455%	$171.1264	$171.13	$171.15	$171.10
Purchase #3	$232.74	10.292%	$256.6936	$256.69	$256.70	$256.70
Purchase #4	$34.90	7.267%	$37.4362	$37.44	$37.45	$37.40
Purchase #5	$122.68	6.813%	$131.0382	$131.04	$131.05	$131.00
Purchase #6	$160.30	12.231%	$179.9063	$179.91	$179.90	$179.90
Purchase #7	$94.79	11.510%	$105.7003	$105.70	$105.70	$105.70
7 purchase totals =	$914.04		$1,000.2432	$1,000.25	$1,000.30	$1,000.10